Fiber cement products are becoming more and more common on construction sites. As such there has arisen a demand for cutting tools, particularly circular saw blades, that can cut this very difficult material, while reducing the amount of fine dust particles generated. A need also exists for such blades that yield a high quality (straight and smooth) cut in fiber cement workpieces. There has also arisen a need for such blades that are less expensive to produce than conventional diamond blades, but which still exhibit good wear characteristics. Finally, there is a perception by users that conventional blades for cutting fiber cement products, particularly blades with conventional tips formed with polycrystalline diamond joined to tungsten carbide (“PCD”) don't “feel” right.
In the conventional manufacturing process, a PCD tip is attached to the rim of the blade blank at four circumferentially equidistant locations, by brazing the carbide portion to the steel blade blank. Frequently, diamond elements are formed and machined, then applied to pre-formed carbide substrates, or, in the alternative, a diamond film is deposited on the carbide tips using a chemical vapor deposition process. One relatively recent process for forming a PCD tip is to cut several parts out of a large PCD blank, in which the PCD has already been fused to a carbide layer or substrate. Another conventional process is to form the PCD tip, braze it to the blade, then machine the radial or side clearances, the tangential clearances, and the top relief or clearance for each tip. In view of the wear resistance inherent in the diamond and carbide materials selected, this amount of machining is a slow, expensive process.
As to the structure of a conventional blade for fiber cement, conventional wisdom dictates using a positive hook angle for the tip. This has not proved to be entirely satisfactory. Further, the conventional design employing four tips doesn't provide a good finish, nor does it provide the user with a good “feel”.